Mario César Mario César - 2 years ago 68
Python Question

How can I load all keys from a dict as local variables, a better aproach?

Giving this dictionary:

>>> options = {'DATABASES': {'default': {'ENGINE': 'django.db.backends.sqlite3'}}}

What would be the best way to get this?:

>>> foo(options)
>>> print DATABASES
{'default': {'ENGINE': 'django.db.backends.sqlite3'}}

I am solving this as locals().update(options), but I was thinking, if there is maybe a better solution.

Answer Source
import inspect

allowed_vars = set(["min_", "max_", "path", ...])
def update_globals(dic):
    caller_frame = inspect.currentframe(1)
    globals = caller_frame.f_globals
    # here, you _could_ simply do globals.update(dic) 
    # but it is  evil
    for key, value in dic.items():
        #here you shuld carefullyt verify each key, and value for not
        #not dangerous pairs, with stuff like:
        #if key not in allowed_vars:
        #    sys.stderr.write("Warning: invalid variable in configuration update\n")
        #     continue
        #if type(value) not in (string, int, float):
        #    #(issue error)
        #    continue
        globals[key] = value


>>> a
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined
>>> update_globals({"a": 5})
>>> a


update 2016-06 A couple of weeks ago I had put together the extradict Python package - it is avalilable on pypi now. One of its features is the MapGetter context manager that allows exactly what is being asked for by doing something along:

from extradict import MapGetter

def myfunc():
    options = {'DATABASES': {'default': {'ENGINE': 'django.db.backends.sqlite3'}}}
    with MapGetter(options) as options:
         from options import DATABASES

And other normal "from .... import .... " usages, but from a dictionary or mapping object (including a default dict).

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